Lubricating grease

ABSTRACT

A LUBRICATING GREASE HAVING A CALCIUM SOAP/SALT COMPLEX THICKENER AND CHARACTERIZED BY OUTSTANDING ADHESIVE QUALITIES, LOW BLEEDING RATE, AND STABILITY AT TEMPERATURES ABOVE 400* F. THE INGREDIENTS FROM WHICH THE GREASE IS FORMED COMPRISE LUBRICATING OIL, A SOURCE OF CALCIUM (SUCH AS HYDRATED LIME), 12-HYDROXY STEARIC ACID, A LOW MOLECULAR WEIGHT ORGANIC ACID, OR A SALT THEREOF, AND ISOBUTYLENE POLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM ABOUT 8,000 TO ABOUT 19,000(STAUDINGER).

United States Patent 3,642,627 LUBRICATING GREASE Roy L. Waring, Moore, 0kla., assignor to Cato Oil and Grease Co. No Drawing. Filed May 31, 1968, Ser. No. 733,240

Int. Cl. Cl0m 5/16' US. Cl. 25239 9 Claims ABSTRACT OF THE DISCLOSURE A lubricating grease having a calcium soap/salt complex thickener and characterized by outstanding adhesive qualities, low bleeding rate, and stability at temperatures above 400 F. The ingredients from which the grease is formed comprise lubricating oil, a source of calcium (such as hydrated lime), l2-hydroxy stearic acid, a low molecular weight organic acid, or a salt thereof, and isobutylene polymer having an average molecular weight of from about 8,000 to about 19,000 (Staudinger).

BACKGROUND OF THE INVENTION Calcium base greases have been widely used in the past because of their ease of manufacture, their structural stability at normal temperatures, and the fact that the ingredients for these greases are relatively economical. Conventional calcium base greases, however, have been useful in services up to only about 200 F. in the past, due to the fact that the small amount of water generally present in such greases is driven olf at temperatures much above 200 F., and the grease then separates into soap and oil with resulting failure of lubrication.

In the prior art, calcium base lubricants which are stable at temperatures considerably in excess of the boiling point of water were developed, and such greases generally contain a small amount of the salt of a low molecular weight organic acid, such as acetic acid. For example, US. Patent No. 2,197,263 describes lubricating greases containing calcium soap and calcium salt of low molecular weight organic acids, which greases have the characteristic of being stable at temperatures of 300 F. and higher.

It is also known that the addition of polymers of isobutylene can be useful in some cases as viscosity index improvers, and the polymers of isobutylene in some cases enhance the adhesive qualities of a grease. For example, US. Patent No. 2,332,825 describes the use of polyisobutylene in a grease composition. More recently, a calcium l2-hydroxy stearic acid thickened grease containing a specific isobutylene polymer was described in US. Patent No. 3,211,650. The greases described therein have been very succesful in most respects, but as in the case of most calcium base greases, they were not suitable for use at elevated temperatures, such as 350 F. or higher.

It would seem therefore, that it would be a relatively simple matter to produce a product possessing the combined desirable properties obtained by use of isobutylene polymers, and by the use of calicum soap/ salt complexes. However, such is not in fact the case, as it was only after extended efforts that the successful compositions and methods of manufacture described herein were developed.

Although no doubt many attempts have been made in the past to overcome the difficulties involved in successfully combining the desirable properties of a calcium soap/salt complex thickened grease and a calcium 12- hydroxy stearic acid grease modified with polyisobutylene, so far as is known, prior to this invention no one has successfully been able to accomplish this, and prior to this invention a successful calcium soap/salt complex ice thickened grease containing polyisobutylene has not been available.

SUMMARY OF THE INVENTION The present invention relates to lubricating greases, and more particularly to calcium soap/salt complex thickened greases containing isobutylene polymer, which greases possess superior properties compared to the greases that have previously been available. The greases of this invention are capable of sticking to metal surfaces in motion even when subjected to sudden shock, and they have dropping points of 400 F. and higher.

The greases of this invention are formulated from ingredients including one or more lubricating oils, a calcium source (generally in the form of hydrated lime, or calcium hydroxide), 12-hydr0xy stearic acid, a source of organic acid radical, such as a low molecular weight carboxylic acid or hydroxy carboxylic acid or a salt thereof, and an isobutylene polymer having an average molecular weight (Staudinger) of between about 8,000 and 19,000. The combined isobutylene polymer and lubricating oils can be varied somewhat and satisfactory below as lubricating fluid.

The improved grease compositions of this invention generally comprise a calcium soap/ salt complex dispersed in a suitable lubricating oil or mixture of oils, which might be a more or less equal mixture of a mid-continent solvent-refined neutral oil having a viscosity of about 350 SUS at 100 F. and a viscosity index of about and naphthenic neutral oil having a viscosity of about 650 SUS at F. It will be obvious to those skilled in the art that the amounts and properties of the above described lubricating oils can be varied somewhat and satisfractory results still obtained; but the above described mixture has been found to produce an excellent lubricant when used with the other ingredients in making the products of this invention. The amount of lubricating fluid (including isobutylene polymer) used, based on the total weight of the lubricant forming ingredients, will be between about 74 and 88 weight percent, and preferably about 82 to 85 weight percent.

The amount of calcium hydroxide which is used in making the lubricants of this invention will generally be from about 3.5 to 5.5 percent based on the total weight of the lubricant forming ingredients. The precise amounts of lime to be used can be calculated from the amounts of l2-hydroxy stearic acid and low molecular weight organic acid which are to be used. Sufficient lime should be used to react completely with all of the 12-hydroxy stearic acid and the low molecular weight organic acid. There should be enough lime in the ingredients to give a strong pink or reddish color when tested with phenolphthalein. If the mixture does not give an alkaline indication when tested after being heated to about 400 F a small amount of lime should be added until the proper pink color is obtained.

The low molecular weight carboxylic or hydroxy carboxylic acid (or salt thereof) which is used should have not more than five carbon atoms, and a preferred low molecular weight acid is acetic acid. Preferably, glacial acetic acid in an amount suflicient to give a weight ratio of between about 0.4 to 1 and 1 to 1 calcium acetate to calcium 12-hydroxy stearate should be used.

The isobutylene polymer should be added in an amount from about 3 to 8 percent based on the total weight of ingredients. In order to obtain equivalent properties in a finished product, it will generally be necessary to use more of the lower molecular weight than the higher molecular weight polymer. For example, about 4 percent of an 18,000 average molecular weight polymer might be equivalent to 7 percent of a 9,000 average molecular weight polymer. If a polymer having an average molecular weight below about 8,000 is used, the amount required to give significant results becomes excessive, while if a polymer having an average molecular weight above about 19,000 is used, it is too diflicult to disperse in the mixture, and can cause damage to the mixing equipment. It is preferred to add the polymer in an undiluted form, rather than as an oil solution of polymer. Preferably, about 4 to 6 percent of polyisobutylene having an average molecular weight of from 10,000 to 15,000 is used.

In some cases it may be desirable to add up to about 4 percent of additives such as anti-oxidation, anti-rust, and/ or extreme pressure ingredients.

The total amount of calcium soap/ salt complex forming ingredients used will range from about 12 to about 26 percent based on the total weight of ingredients. In other words, the total amount of hydrated lime, 12- hydroxy stearic acid, and low molecular weight organic acid will be in this range, although the total weight of complex in the finished product may be slightly less due to water splitting out during the manufacture of the lubricant. It is desirable to keep the amount of complex in the finished product as low as possible, and still retain the desired properties of the lubricant. The yield of the finished product is related to the amount of complex in it, a high yield product having a low amount of complex, and a low yield product having a high amount of complex.

The improved lubricating greases of this invention can be manufactured according to more or less conventional techniques. For example, an initial portion of the lubricating oil, which might be about one-half of the total lubricating oil, is mixed with the hydrated lime and stirred until a uniform mixture is obtained. The 12- hydroxy stearic acid is then stirred in, and the resulting mixture is heated up to at least 190 F. for about 30 minutes. It is preferred in this initial heating to take the mixture to about 250 F. to eliminate the water therefrom. Elimination of water is desirable in that it will reduce rusting of the equipment, particularly if stainless steel equipment is not being used. The heated mixture is then cooled, by addition of the remaining lubricating oil, to about 150 F. or cooler. At this point, the low molecular weight organic acid or salt thereof is added, and the resulting mixture stirred without heating for at least 30 minutes. In the case of acetic acid, when using open vessel processing (at atmospheric pressure), it cannot be added at temperatures above about 150 F. or it will partially evaporate before it has a chance to react and form the soap/salt complex. It is also somewhat hazardous to handle acetic acid at high temperature due to its low flash point. After addition for at least 30 minutes, and then heated rapidly to about 400 F. When the mixture has reached 400 F., it is checked for alkalinity with phenolphthalein. If a fairly strong pink color is not obtained, a small amount of lime can be added and the alkalinity rechecked after stirring for a few minutes. The mixture is held at about 400 F. for a period of fifteen minutes to one hour, with continuous stirring. The mixture is then cooled down to about 250 F. to 300 F., and the polyisobutylene is added to the mixture. The mixture containing the polyisobutylene is then stirred until the polymer is uniformly dispersed throughout the mixture. If an additive is to be used in the finished product, it is added after the mixture has further cooled to about 200 F. or lower. The grease is then milled, de-aerated and checked for penetration, consistency, and other specifications.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is a description of the method of preparing a lubricating grease in accordance with a preferred embodiment of this invention. In Table I below are listed the ingredients for this particular composition, and the process of preparing the product is then described.

4 TABLE I Ingredient: Amount Naphthenic neutral oil650 SUS at 100 F gallons 520 Hydrated lime pounds 442 12-hydroxy stearic acid pounds 1,012 Parafiinic solvent-refined neutral oil-VI- 350 SUS at F. gallons 520 Glacial acetic acid pounds 433 Polyisobutyleneaverage molecular weight 11,000 pounds 500 Additive (anti-oxidant and extreme pressure pounds 100 In preparing the lubricant in accordance with this preferred embodiment, all of the hydrated lime is added to 200 gallons of the naphthenic oil and stirred until the mixture is uniform. All of the 12-hydroxy stearic acid is then blended into the mixture and the resulting mixture is heated up to about 250 F. and held at this temperature for 30 minutes. The remainder of the naphthenic oil and all of the paraffinic oil are then added to the heated mixture to cool it. All of the acetic acid is then added to the cooled mixture (provided that it is F. or cooler), and the mixture is stirred without heating for 30 more minutes. The mixture is then heated with continued stirring up to 400 F. When 400 F. is reached, the alkalinity of the mixture is checked with phenolphthalein. If it does not give a strong pink color, three pounds of additional hydrated lime are mixed into a small amount of oil and added to the mixture. It is held at 400 F. for a total of one hour, and then cooled with continued stirring down to about 350 F. After the mixture has cooled on down to 275 F., all of the polyisobutylene is added and stirred into the batch. The batch is blended until it has cooled to below 200 F., and then the additive is added. The resulting grease is milled and de-aerated, and then is checked to see that it meets all specifications, in which case it is packaged for use.

In accordance with another preferred embodiment of the invention, the ingredients listed below in Table II are used in manufacturing a grease according to the process as described below.

TABLE II A Amount Ingredient: (Parts by weight) Naphthenic oil-750 SUS at 100 F. 35.0 Hydrated lime 4.6

at 100 F. 35.0 12-hydroxy stearic acid 10.9 Glacial acetic acid 5.2 Polyisobutylene (average molecular weight 11,000) 7.2 Additive (anti-oxidant and extreme pressure) 2.5

The process of making a grease from the above ingredients involves adding 2 parts of hydrated lime to 10 parts naphthenic oil and stirring to obtain a uniform blend. Then add 5 parts naphthenic oil, 15 parts parafiinic oil, and 10.9 parts of 12-hydroxy stearic acid. The resulting mixture is heated to 250 F. to form a calcium stearate soap and to dehydrate the mixture. After 30 minutes heating, 20 parts of naphthenic oil and 20 parts of paraffinic oil are added to cool the mixture down to about 210 F. The mixture is allowed to cool on down to about 180 F. and 2.6 parts of lime are blended in. 5.2 parts of glacial acetic acid are added and stirred to obtain thorough mixing. The mixture is then heated rapidly with stirring to 400 F. and held at this temperature for about 30 minutes. The mixture is allowed to cool to about 275 F., and 7.2 parts of polyisobutylene are then added with continued stirring. The mixture is allowed to cool on down to about 200 F at which point 2.5 parts of additive is added and blended in. The grease is then put through a colloid mill and de-aerated, and after checking to see that it meets specifications, it is packaged for use.

In accordance with another preferred embodiment of the invention the ingredients listed below in Table III are used in manufacturing a grease by processes similar to those described above.

TABLE III Amount Ingredient: (Parts by weight) 12-hydroxy stearic acid 8.2 Glacial acetic acid 3.6 Hydrated lime 3.7

Polyisobutylene (average molecular weight 11,000) 4.7 600-650 SUS at 100 F. naphthenic oil 77. Additives 2.5

In accordance with still another preferred embodiment of the invention, the ingredients listed below in Table IV are used in manufacturing a grease by processes similar to those described above.

It is understood that the above examples of preferred embodiments are illustrative, and are not to be considered as limiting the scope of the invention:

I claim:

1. A calcium soap/salt complex thickened lubricating grease comprising:

(a) between 74 and 88 percent of lubricating fluid, including between 3 and 8 percent of isobutylene polymer having an average molecular weight of from 8,000 to 19,000; and

(b) between 12 and 26 percent of a calcium soap/salt complex of 12-hydroxy stearic acid and a low molecular Weight organic acid selected from the group consisting of carboxylic and hydroxy carboxylic acids having not more than five carbon atoms, the weight ratio of calcium salt of low molecular weight organic acid to calcium 12-hydroxy stearate in the complex being between about 0.4 and 1.0 to 1.

2. The lubricating grease of claim 1 in which the low molecular weight organic acid is acetic acid.

3. The lubricating grease of claim 2 in which the isobutylene polymer has an average molecular weight of 10,000 to 15,000 and is present in an amount of from 4 to 6 percent.

4. The lubricating grease of claim 3 in which that portion of the lubricating fluid which is not isobutylene polymer is comprised of approximately equal portions (by volume) of a solvent-refined paraffinic neutral oil having a viscosity of about 350SUS at 100 F. and a viscosity index of about 95, and a naphthenic neutral oil having a viscosity of about 650 SUS at 100 F.

5. The lubricating grease of claim 3 in which that portion of the lubricating fluid which is not isobutylene polymer is comprised of a naphthenic oil having a viscosity of about 600-650 SUS at 100 F.

6. The lubricating grease of claim 3 in which that portion of the lubricating fluid which is not isobutylene polymer is comprised of about 40 percent by volume of solvent-refined parafiinic neutral oil having a viscosity of about 600 SUS at 100 F., and a viscosity index of about 95; the balance of the lubricating fluid being a naphthenic neutral oil having a viscosity of about 650 SUS at 100 F.

7. The lubricating grease of claim 4 including 0.5 to 4.0 percent of additives comprising anti-oxidant, anti-rust and extreme pressure agents.

8. The lubricating grease of claim 7 in which about percent by weight of the grease is lubricating oil, about 4.5 to 5.0 percent is isobutylene polymer, and about 18 percent is calcium 12-hydr0xy stearate/acetate complex.

9. A process of manufacturing a calcium soap/ salt complex thickened lubricating grease from ingredients consisting essentially of: 9-10 percent 12-hydroxy stearic acid; 4.0-4.2 percent glacial acetic acid; 4.0-4.5 percent hydrated lime; 36-39 percent paraflinic solvent-refined neutral oil having a viscosity of about 350 SUS at 100 F. and a viscosity index of 36-39 percent naphthenic neutral oil having a viscosity of about 650 SUS at F.; 4.5-5.0 percent of an undiluted isobutylene polymer having an average molecular weight of 10,000 to 12,000; and up to 4.0 percent additives comprising anti-oxidant, anti-rust and extreme pressure agents comprising the step of:

(a) mixing the hydrated lime and l2-hydroxy stearic acid with a portion of the naphthenic oil, heating the resultant mixture to about 250 F. and maintaining this temperature for about 30 minutes;

(b) adding the paraffinic oil and the remainder of the naphthenic oil to cool the mixture;

(c) adding the acetic acid and stirring without heating for about 30 minutes;

((1) heating to about 400 F. and maintaining this temperature for at least one hour;

(e) after the mixture has cooled to about 275 F., adding and blending in the isobutylene polymer; and

(f) adding and blending in the additives.

References Cited UNITED STATES PATENTS 2,197,263 4/1940 Carmichael et a1. 252-405 2,332,825 10/ 1943 Zimmer 252-407 2,846,392 8/1958 Morway et al. 252-39 3,211,650 10/1965 Oswalt 252-39 3,271,311 9/1966 Morway et al. 252-59 3,361,669 l/l968 Van Westen et al 252-59 DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner US. Cl. X.R. 252-59 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 7 Dated February 15, 1972 Inventor(s) R037 L. Waring It is certified that error appears in the above-identified patent .and that said Letters Patent are hereby corrected as shown below:

Column-2, line 23, reads "lubricating oils can bevaried somewhat and satisfactory". It should read lubricating oil or oils is referred to in a some instances Column 3, line 51, after "addition" add the line of the low molecular weight organic acid,- the mixture is stirred' cold Signed and sealed this 13th day of June 1972-.

Attest:

EDWARD M.FLET CHER, JR. ROBERT GOTTSCHALK Attesting Officer Y Commissioner of Patents FORM PC4050 (10459) USCOMM-DC 6O376-P59 US. GOVERNMENT PRINTING OFFICE: 369 0-358'33 

